Washington: The United States on Tuesday urged Nigeria to go forward with planned February 14 presidential and legislative elections, despite being hit with "horrific" attacks by Islamist group Boko Haram.

The State Department declined to give any specific figures Tuesday for the number of victims in an offensive by the group in the northern region of Baga, on the banks of Lake Chad.

"We`re still trying to get more confirmation of the death toll," deputy spokeswoman Marie Harf said.

However, she added that "there has been a sharp escalation in the number of reported casualties."

Boko Haram launched a first assault on Baga, in the northern part of Borno State, on January 3, before coming back several days later and razing the city along with around 15 villages around it.

Local officials have reported a high number of deaths, but there is no confirmed death toll.

The Nigerian military Saturday said it was "appropriate" to consider the Baga offensive the deadliest since the start of the Islamist insurrection, which has killed 13,000 people since 2009.

"We`ve obviously all seen the reported number shift this week, which we can`t confirm exactly, but, you know, it clearly shows there`s been a sharp escalation," Harf said.

The US official, whose government is allied with Nigeria in the fight against Boko Haram, reiterated the call for the presidential and legislative elections not to be delayed.

"We do think that the election is probably a factor" in the violence in northeastern Nigeria, but "we believe the election should still go forward even in the face of this pretty horrific violence," the spokeswoman said.

On Tuesday, Nigeria`s electoral commission said the votes will go ahead in three northeastern states worst hit by Boko Haram violence but warned there was little prospect of voting in militant-held areas.

There are a total of 14 presidential candidates, including incumbent Goodluck Jonathan and former dictator Muhammadu Buhari, contesting the February 14 presidential poll. The legislative votes are to be held the same day.